netdev - Re: [PATCH 2/3] powerpc: bpf: flush the entire JIT buffer

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Message-ID: <20170113201055.GB60330@ast-mbp.thefacebook.com>
Date:   Fri, 13 Jan 2017 12:10:56 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        netdev@...r.kernel.org, ast@...com, daniel@...earbox.net,
        davem@...emloft.net
Subject: Re: [PATCH 2/3] powerpc: bpf: flush the entire JIT buffer

On Fri, Jan 13, 2017 at 10:40:01PM +0530, Naveen N. Rao wrote:
> With bpf_jit_binary_alloc(), we allocate at a page granularity and fill
> the rest of the space with illegal instructions to mitigate BPF spraying
> attacks, while having the actual JIT'ed BPF program at a random location
> within the allocated space. Under this scenario, it would be better to
> flush the entire allocated buffer rather than just the part containing
> the actual program. We already flush the buffer from start to the end of
> the BPF program. Extend this to include the illegal instructions after
> the BPF program.
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Acked-by: Alexei Starovoitov <ast@...nel.org>